There's no computers in it, but Coppola's "The Conversation" is a classic - http://en.wikipedia.org/wiki/The_Conversation - it's about electronic surveillance. There's a great scene near the end that reminds me of debugging - the wikipedia article has a picture and descriptive caption of that scene:
"At the end of The Conversation, Gene Hackman, as paranoid audio surveillance expert Harry Caul, plays the saxophone in his apartment, which he took apart piece by piece trying to find a bug. The scene vividly illustrates Caul's complete emotional isolation by having him literally tear away practically every vestige of the material world that surrounds him, shattering the safety and security of his carefully-constructed womb."
"At the end of The Conversation, Gene Hackman, as paranoid audio surveillance expert Harry Caul, plays the saxophone in his apartment, which he took apart piece by piece trying to find a bug. The scene vividly illustrates Caul's complete emotional isolation by having him literally tear away practically every vestige of the material world that surrounds him, shattering the safety and security of his carefully-constructed womb."